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Thread: 670 Avenger off idle issues.

  1. #1
    Join Date
    May 2018
    Location
    Monroe OH
    Posts
    4

    Default 670 Avenger off idle issues.

    '95 351W stock internals, RPM intake with 1" 4 hole spacer, shorties, HEI distributor set @ 10° initial, 18° mechanical, all in by 3200. (Adjustable advance canister can add up to 20°, but set stingy for cheap gas. Plugged for carb testing, maybe get more into once carb nailed down.) C6 stock convertor, 3:25 gears, 31 tires. '71 F100 hobby, spare truck, focus on smooth driveability over time slips or strict MPG.
    Retail sold 670 Street Avenger about 3 years ago, 65/68 jetting, 6.5 power valve, 31 boosters, floats set on vehicle, idle screws 1.5 out, slots verified, accelerator linkage verified (new metal arm kit), 1/2 turn off base idle screw to get smooth idle at 750 in gear, 20 inHg vacuum. Overall power and mileage, not bad, secondaries with middle spring pull strong. Runs well on this setup overall except for soggy lower end. Never backfired, but feels like a hole in accelerator side I can't get right. Cruise vacuum in mid teens steady drops to 10 inHg on quick mid throttle pull. WOT from dead stop is hard and clean, plugs clean dark brown, never black or wet. Only detonation on 87 a few days temps and humidity had been very high, otherwise has run really well on regular. Low end stumble on medium throttle. Best example is slowing to turn on a street at 20 MPH, will gasp 1/2 a second and hit, sometimes will drop enough in vacuum for transmission to downshift (detent cable not even close), orange cam in #1 hole. Went 31 to 35 nozzle (no real change). Leaks, manifold flanges, slots square, linkages, timing, pressure, filters, all the usual items checked and inline.
    Last edited by Tony Lainhart; 07-16-2020 at 08:50 PM. Reason: gave wrong info first post

  2. #2
    Join Date
    May 2018
    Location
    Monroe OH
    Posts
    4

    Default

    UPDATE: Installed Proform street metering block (primary side) jetted up to 68s & 72s. Super smooth idle with mix screws one turn out as opposed to 1.5, great throttle response and stumble GONE.

  3. #3
    Join Date
    Jan 2010
    Location
    Brisbane, Australia
    Posts
    1,944

    Default

    Sounds like a lean idle circuit. Mixture screws out less now says the IFRs are richer in the Proform block, hence the part throttle stumble gone. Many changes at the same time, be careful.
    Regards, Gary

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